ICQ was the location of the only (I hope) successful phishing attack against me. I hadn't used my account for a significant amount of time, and I received an e-mail asking me to sign-in and update my password. Foolishly, I clicked on the link and logged in to a legitimate looking website. Not long afterwards, I no longer had any access to my account. I'm still not sure what they wanted from my account, other than my fairly low (6 digit) UIN.
I wish I could reclaim my ICQ account. I was inactive for way too long, and the account recovery process is apparently inaccessible to me (along with whatever e-mail I had registered to it, I'm sure).